Re^3: win32, ctrl-c, sleep, and signals

[BrowserUk]

You have to remember that Win32 does not have signals as a native concept. Perl's support for them is simulated and limited, and is actually implemented via the process message queue. This is the code that implements the signal emulations from win32.c:

void
sig_terminate(pTHX_ int sig)
{
    Perl_warn(aTHX_ "Terminating on signal SIG%s(%d)\n",PL_sig_name[si
+g], sig);
    /* exit() seems to be safe, my_exit() or die() is a problem in ^C 
+thread */
    exit(sig);
}

DllExport int
win32_async_check(pTHX)
{
    MSG msg;
    int ours = 1;
    /* Passing PeekMessage -1 as HWND (2nd arg) only get PostThreadMes
+sage() messages
     * and ignores window messages - should co-exist better with windo
+ws apps e.g. Tk
     */
    while (PeekMessage(&msg, (HWND)-1, 0, 0, PM_REMOVE|PM_NOYIELD)) {
        int sig;
        switch(msg.message) {

#if 0
        /* Perhaps some other messages could map to signals ? ... */
        case WM_CLOSE:
        case WM_QUIT:
            /* Treat WM_QUIT like SIGHUP?  */
            sig = SIGHUP;
            goto Raise;
        break;
#endif

        /* We use WM_USER to fake kill() with other signals */
        case WM_USER: {
            sig = msg.wParam;
        Raise:
            if (do_raise(aTHX_ sig)) {
               sig_terminate(aTHX_ sig);
            }
            break;
        }

        case WM_TIMER: {
            /* alarm() is a one-shot but SetTimer() repeats so kill it
+ */
            if (w32_timerid && w32_timerid==msg.wParam) {
                KillTimer(NULL,w32_timerid);
                w32_timerid=0;
            }
                else
                    goto FallThrough;
            /* Now fake a call to signal handler */
            if (do_raise(aTHX_ 14)) {
                sig_terminate(aTHX_ 14);
            }
            break;
        }

        /* Otherwise do normal Win32 thing - in case it is useful */
        default:
        FallThrough:
            TranslateMessage(&msg);
            DispatchMessage(&msg);
            ours = 0;
            break;
        }
    }
    w32_poll_count = 0;

    /* Above or other stuff may have set a signal flag */
    if (PL_sig_pending) {
        despatch_signals();
    }
    return ours;
}

Setting the environment variable PERL_SIGNALS=unsafe allows ^C to interupt sleep. Without it, the signal handler doesn't get invoked until the sleep is over.